I don't have a web site. If you search my name on this site, you will see some pictures of a bari sax neck I made. and a 28M key guard I make.You can also see some pictures of things I've made(not just instrument parts) on the Photobucket web site under the name slausonm .
As Steve mentioned in a previous post there is a lot of fitting... to making a key. There is no magic, although some people would have you think there is. It takes basic metal working skills and some machinery. I started working on metal lathes when I was in the 7th grade and have been making things on them and other machinery since. I'm 46 you can do the math. When I am not fixing instruments and teaching, I've been making my own CNC machinery.
My process goes like this: LOOK at the other keys and mechanisms to determine function and style. (have a plan) Measure things like pad cup and hinge rod diameters with a micrometer or dial caliper to an accuracy of .001" . I generally make the pad cup first. Depending on the size , this can be turned on a metal lathe or formed out of a sheet of brass. I will then generally make a plug to fit in the tone hole that will center the new pad cup for fitting the lever. Next is the hinge tube or rod. If it is solid(rod) then I take a rough measurement between posts and rough cut the material. I chuck it in my lathe and face the ends until it fits perfectly between the posts. The ends of the rods are then center drilled and then reamed to fit the pivot screws in the horn. If it is a hinge tube I either make a tube if it is short like in palm keys or purchase tubing as close to the original size as possible, then do what I have to to fit it correctly. Next are the lever parts of the keys this takes a lot of checking and fitting, milling filing... Too much to explain in detail. Then silver solder parts and more fitting, Then drill and tap for spring screws, then polish and lacquer or plate. Simple as that. :)
Xequenze, I could probably make one that would come close to fitting but I would need detailed measurements and good pictures. If you are skilled with fitting keys you could probably finish it off, if not you would have an expensive piece of scrap brass to admire. Send me a picture and some rough measurements to my e-mail address and I will let you know if I think it can be done from thousands of miles away.